1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer and the like, and more particularly, it relates to an image forming apparatus (referred to as "copying machine" hereinafter) including a sheet containing device (referred to as "cassette" hereinafter) for accommodating a plurality of sheets, which cassette is removably arranged within the copying machine.
2. Related Background Art
In the past, a copying machine including a cassette (for accommodating a plurality of sheets) removably mounted within the body of the machine has already been known. In such conventional copying machine, a friction pad or a retard roller is used as a sheet separating means. Further, such copying machine is designed so that a jammed sheet can be removed by retracting it toward a sheet feeding direction (refer to FIG. 8A).
However, in such conventional copying machine, there arises a problem that, when the jammed sheet is pulled toward the sheet feeding direction to remove it, a next sheet adjacent to the undersurface of the jammed sheet is often shifted together with the pulled sheet to abut against the sheet separating means, thus bending the next sheet (refer to FIG. 8B). In order to solve such problem, a copying machine wherein when the jammed sheet is removed the sheet separating means is retarded or retracted from the sheet feeding path has been proposed.
In such copying machine, there is an advantage that when the cassette is extracted toward a direction opposite to the sheet feeding direction any sheet does not remain on the sheet separating means (refer to FIG. 8C); however, there arises a drawback that, when the jammed sheet is pulled or extracted toward the sheet feeding direction, since the friction force between the stacked sheets is increased by the pressing action of the sheet feed roller, sheets positioned below the jammed sheet are successively shifted in response to the pulling action of the jammed sheet (refer to FIG. 8D).